Sinkhole risk in Garrett County, MD: Mostly deep or small

Mostly deep or small

Some soluble rock, mostly deeply buried or in a small share of the county.

On soluble rock: 8%
At or near the surface: 8%
Buried under cover: 0%

What to do about a house in Garrett County

Sinkholes are uncommon here; watch for new depressions after heavy rain or leaking pipes.

That works out to roughly 50 of Garrett County's 649 square miles on soluble rock, 50 of them with the rock at or near the surface. With about 28,393 residents (44 per square mile), much of the land is open, and the mapped rock may sit far from where people actually live. The figures come from 247 map points about 1.6 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Garrett County

The nearest county rated sinkhole country is Winchester city, VA, about 64 miles southeast. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Mineral County, WV 20 mi southeast · 12% at surface
Preston County, WV 22 mi west · 2% at surface
Allegany County, MD 31 mi east · 24% at surface
Grant County, WV 31 mi south · 11% at surface
Fayette County, PA 32 mi northwest · 23% at surface
Somerset County, PA 33 mi northeast · 5% at surface

What Garrett County is built on

The largest mapped soluble unit here is the Greenbrier Formation (shale), Mississippian in age, covering about 7% of the county. Next is the Monongahela Formation at under 1%.

The county also lies over the Michigan Basin; Ohio Basin; Appalachian Basin, a deep salt or gypsum basin. Deep beds rarely cause surface collapse on their own, but wells and mining into them have.

Against the rest of Maryland

Garrett County ranks 10 of 24 in Maryland for soluble rock at the surface, and sits above 66% of US counties on that measure.